This month's rankings represent a changing of the guard -- two guards, in fact. Both the men's and women's pound-for-pound rankings have new No. 1s, as Jon Jones and Amanda Nunes take over the top spots on the strength of their Dec. 29 wins.

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The Nunes ascension is a no-brainer, after her 51-second destruction of former No. 1 Cris "Cyborg" Justino left our voters no other reasonable choice. But among the men, Jones moving up from No. 4 was a tougher call, because his victory over Alexander Gustafsson came in Jones' return from suspension for a failed drug test. And the reigning No. 1, Daniel Cormier, was ESPN's Fighter of the Year for 2018.

Here is how our voters arrived at their decisions.

Okomoto, who voted for Jones at No. 1 (after having previously reintroduced him to the Top 10, at No. 2, after Jones' suspension ended in October): "As the famous saying goes, 'Pound-for-pound rankings are in the eye of the beholder' -- and my criteria for these rankings is pretty simple. This is about one thing and one thing only: identifying the best fighter in the world. And if my life depended on picking a winner in any MMA fight imaginable, I'm taking Jon Jones. That's it. I had Daniel Cormier at No. 1 before last week, but after seeing the ease with which Jones beat Alexander Gustafsson -- the man responsible for the closest fight of his career -- I can't rank him as anything but No. 1."

Helwani, who voted to keep Cormier at No. 1 and put Jones right below (after not having had Jones in his Top 10 previously, even after the suspension was over): "I wanted to wait until Jones actually fought before including him in my rankings. And if UFC 232 happened controversy-free, I would have probably put him No. 1. However, I now want to wait and see how things play out in Nevada. I know that doesn't necessarily make sense, but since pound-for-pound rankings are so subjective anyway, my rankings, my rules."

Editor's Picks

Amanda Nunes added the featherweight title to her bantamweight belt with a 51-second KO of Cris Cyborg on Dec. 29.

Wagenheim, who has had Jones at No. 1 ever since the suspension ended: "The minute he was eligible to fight, I felt there was no place to put Jones but at the top of the rankings. He's the greatest ever to set foot in the Octagon, and he beat up Cormier twice to prove it. Yes, one of those fights ended up as a no contest because of a drug test failure, and it's fair to factor that in, but if Jones is in my Top 10, he's got to be No. 1."